The primary objectives of this research project are to determine prospectively the extent to which structural and functional aspects of social support influences "hard" cardiac events (death, non-fatal myocardial infarction) in patients with coronary artery disease (CAD) and to identify the behavioral and biological mediators of these influences. Social support will be assessed in a large consecutive cohort of coronary disease patients referred for diagnostic catheterization (Group A) and in a subgroup of medically treated patients with severe CAD and/or poor left ventricular function with an expected greater than or equal to 25% two year "hard' cardiac event rate (death or nonfatal MI) (Group B). A brief baseline questionnaire assessment of structural and functional aspects of social support as well as other aspects of quality of life will be obtained on all CAD patients without prior revascularization who are referred to the Duke University Cardiac Catheterization Laboratory over a three year period (Group A). Detailed questionnaire and interview assessment of social support(perceived and received) and psychological traits (i.e., hostility) will be obtained on a high risk subgroup (Group B) and a randomly selected 10% subgroup of other Group A patients. Potential behavioral (i.e., smoking behavior, physical activity, medical care utilization) and biological (i.e., vagal tone, ambulatory ischemic burden) mediators of the social support effects on outcomes will be measured in Group B patients and the random subset of Group A. Group A patients will be followed by mailed questionnaire at three months and one year and then annually. Group B and the random subset of Group A will return for a one month clinic visit. At that time, repeat social support interviews will be administered and patients will be sent home with a 48 hour ambulatory ECG monitor to allow measurement of total ischemic burden and heart rate variability (vagal tone). Group B patients and the random subset of Group A will then be followed by telephone interview at one year and then annually. In addi- tion, these patients will have brief bimonthly telephone contacts to assess interval changes in social support as well as levels of environmental stress and mood states (including depression and anger). All patients will be followed for up to three years. Outcome events, including death and myocardial infarction, will be ascertained at each point in follow-up. Multivariable analyses using the spline proportional hazards regression model will test the prognostic importance of the social support and psychological measures on outcome and will evaluate the role of biological and behavioral variables as mediators, controlling for baseline disease severity. Besides extending our understanding of the mechanisms of social support effects on health, the findings of this project will help in the design and development of more effective and efficient approaches to secondary prevention in CAD. This is a revised submission of HL 45702.